1. Field of the Invention
The present invention relates to a condom article and method for making the same.
2. Description of the Art
In recent years, there has been a significant increase in the incidence and spread of sexually transmitted diseases, and this phenomenon has in turn caused an increased use of condoms as a prophylatic measure to reduce the risk of infection and transmission of such diseases.
Among the reason for the increase in incidence and rate of transmission of sexually transmitted diseases (STD's) are the development of increasingly antibiotic-resistant strains of disease-causing organisms, e.g., those responsible for diseases such as syphillis and gonorrhea. Another factor has been the absence of any effective cure for acquired immunodeficiency syndrome (AIDS).
Recent disclosures by the Centers for Disease Control (Washington and Atlanta), and reports at the Third International AIDS Conference in Washington, D.C. in June, 1987, have focused international attention on the proliferation of acquired immunedeficiency syndrome (AIDS) in the general population, beyond the originally defined high-risk classification groups of homosexuals, bisexuals, intravenous drug users, and Haitain/African groups.
The diseases with which AIDS has been or is suspected to be linked include Pneumocystis carinii pneumonia, Kaposi's sarcoma, esophageal or bronchopulmonary candidiasis, extrapulmonary cryptococcosis, cytomegalovirus internal organ infection, disseminated Mycobacterium avium complex or M. kansasii infection, chronic herpes simplex ulceration, chronic cryptosporidiosis enteritis, toxoplasmosis of the brain, high-grade B-cell non-Hodgkin's lymphoma, disseminated histoplasmosis, chronic isosporiasis enteritis, and lymphoid interstitial pneumonia in children.
In a recent San Franciso cohort study reported in "AIDS: The Cost in Health and Lives," Selik, M. D. Richard M., et al, The Internist, April, 1987, p.p. 6 et seq., there was found to be, for every case of AIDS in the group studied, nine cases of other HIV-related morbidity. As also indicated in this article, cohort follow-up studies indicate that the proportion of HIV-infected persons who will ultimately develop AIDS ranges from 25% to 50% or more depending on the length of follow-up and the patient's clinical status at the beginning of the study. Mathematical modeling of this trend in reported AIDS cases has led to a projection that the cummulative total of AIDS cases will be 270,000 by 1991, and the number reported that year alone will be 74,000.
Against the foregoing background, and the recognition that condoms afford a safe, low cost, and generally reliable means for combating the spread of STD's, including AIDS, there has been an increased demand for condoms in developed, as well as developing countries, where some governments are distributing condoms to their citizens at no charge, to minimize the spread of STD's. As a result of the mass distribution of condom products, there is a need in the industry for the development of low cost, storage-stable condoms which are readily and simply produced in mass quantities, by methods and apparatus entailing low capital investment requirements.
Currently, most condoms are produced from a latex resin via a dipping process in which a cylindrical and rounded-end mold is dipped into a resin bath, so that the mold is coated with a thin layer of the latex material. The thickness of the latex coating on the mold is dependent on the viscosity of the latex, and the speed of extracting the mold from the latex bath. Similar latex dipping processes have been employed with suitably shaped molds to form tight-fitting gloves such as surgical gloves.
The above-described latex resin dipping process has been utilized for decades, and yields a generally satisfactory barrier product at reasonable cost.
With the recent spread of AIDS in the general population and the resurgence of condom usage in sexual activities, there has been interest in improving the strength and reliability characteristics of condoms, and of achieving improvements in manufacturing processes and economics, to further combat the spread of STD's generally, and AIDS specifically, as well as to provide a safe and reliable contraceptive means.
U.S. Pat. No. 4,576,156 issued Mar. 18, 1986 to Manfred F. Dyke discloses a condom formed of a thermoplastic polyurethane material, having a generally cylindrical configuration with an open proximal end and a closed distal end. The disclosed condom has a thickness of from about 0.01 millimeters, or less, to about 0.25 millimeters. The thermoplastic polyurethane employed to form the condom is disclosed as having: an average Shore A hardness of from about 50 to about 90; a tensile stress, at 100% of elongation, between about 300 and 1,000 psi; and a tensile stress, at 300% elongation, between about 800 and 3,000 psi. Suitable thermoplastic polyurethane species for manufacturing the condom include those set out at column 2, line 55 to column 3, line 10 of the Dyke patent, with polyether--or polyester--based urethane elastomers said to be preferred. In the manufacture of the thermoplastic polyurethane condom disclosed in the Dyke patent, a film of the polyurethane material, e.g., in the form of a 6-inch square, is heated to a temperature high enough to soften the polymer but low enough to avoid chemical degradation, preferably in a clamping frame, and at a temperature of about 400.degree.-500.degree. F. The heated film then is brought into contact with a preformed mandril to cause the film to assume the shape of the mandril, preferably with application of a vacuum to the system in order to bring about uniformity in wall thickness (column 3, lines 47-50 of the patent).
In an illustrative example described at column 4, lines 22-38 of the Dyke patent, an extruded film of Pellethane.RTM. X5036-80AA polyurethane (The UpJohn Company, Kalamazoo, Mich.) is clamped on a clamping frame and heated at 460.degree. F. for 180-200 seconds, following which vacuum is drawn on the film and the mandril moved downward into the film. Vacuum is shut off as the mandril moves into the film, then is applied at the base of the mandril after it has moved down into the film completely, such vacuum causing the film to pull down tightly and assume the shape of the mandril. After 30-100 seconds of vacuum forming in this manner, the vacuum is released, excess material at the base is cut off, and the film is partly rolled up onto itself for a distance of about 3 inches, on the 10-inch mandril, and then is dusted with powder and rolled up until it is removeable from the mandril.
Although the Dyke patent describes the condom product as having substantially uniform wall thickness, it will be recognized that the deformation of the thermoplastic polyurethane sheet with the heated mandril will inherently cause stretching and localized stresses and thinning, which in turn will cause non-uniformity of thickness over the entire areal extent of the condom article. Further, the nature of the deformation process using the preheated mandril is such that localized thermal stresses and temperature gradients will be developed, which may significantly adversely affect the strength and use characteristics of the condom product. In addition, the cutoff of excess material at the base of the mandril following the forming operation will result in significant wasteage of material and/or the necessity to rework such material in the process system. Finally, the use of small units of the polyurethane film, such as the 6-inch squares disclosed in the patent, entails significant disadvantages in terms of materials handling and the processing of the film stock, and may also entail significant material wasteage and/or reworking of material.
European patent application 0 147 072 published Jul. 3, 1985 in the names of Robert A. Taller, et al, discloses a process for making a polyurethane condom with a uniform thickness of from about 1.5 to about 4 mils. A heat cured polyurethane prepolymer solvent solution is employed into which a mold is dipped and withdrawn for heat curing on the mold. The polyurethane prepolymer which is employed in the dipping medium is a prepolymer which is the reaction product of a polyisocyanate with at least one long chain polyol. The polyol is amorphous at room temperature, has an average molecular weight of from about 500 to about 5,000, a hydroxy number of from 225 to about 22.4, and a NCO/OH ratio of from about 0.95:1 to about 1.1:1.
The above-described process suffers the deficiencies inherent in all resin bath dipping methods for forming condoms, including slow processing times on a unit product basis, so that many dipping systems must be provided and concurrently operated to achieve high volume production.
For example, the European application states at page 7, line 18, that the condom mold may be dipped into and withdrawn from the polyurethane solution at a rate of about 16 to about 90 centimeters per minute; lines 25-27 at the same page of this application indicate that the dwell time of the condom form in the polyurethane prepolymer solution is on the order of from about 20 to about 70 seconds.
Once the mold is withdrawn from the solution, the polyurethane film deposited on the dipped form is air dried and then cured at elevated temperature, e.g., between about 130.degree. C. and about 175.degree. C., for about 20 to about 40 minutes, as disclosed at page 7, lines 33-35 of the application.
The polyurethanes employed in the process of the European patent application are segmented block copolymers constituted by alternating sequences of hard rigid segments and soft, flexible segments, in which the hard segment and the degree of crosslinking are balanced within the ranges of approximately 14-25 percent hard segment and approximately 5,000-30,000 molecular weight per cross link. The application states that the polyurethane polymers employed in the disclosed process provide a Shore A durometer hardness of about 35 to 60. Page 10, lines 19-22 of the application state that representative polyurethane polymers comprise from about 13% to about 23% isocyanate, from about 70% to about 84% long chain diol, and from about 0.75% to about 6% of a crosslinker.
A further disadvantage of the process of this European application is that the polyurethane prepolymer is utilized in solvent solution. Methylene chloride is disclosed as particularly convenient in such usage. The patent application discloses at page 15, lines 35-38 that the resin solution is maintained at a temperature between about 15.degree. and about 25.degree. C. to control viscosity and help prevent evaporation of the volatile solvent. Accordingly, the resin solution and the condom forms must be maintained at a low temperature to minimize loss of volatile solvent from the dip coating system.
It is accordingly an object of the present invention to provide an improved condom which is readily, simply, and inexpensively formed.
It is another object of the invention to provide a method for forming a condom of such type, which facilitates mass production of the condom.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.